A. R. McGhie, J. E. Fischer, P. A. Heiney, P. W. Stephens, R. L. Cappelletti, D. A. Neumann, W. H. Mueller, H. Mohn and H.-U. ter Meer, Phys. Rev. B49, 12614-12618 (1994).
Modulated differential scanning calorimetry of sublimed C70 shows clear evidence for 4 first-order transitions, 2 strong and 2 weak, which we associate with the two different molecular rotational degrees of freedom in majority (equilibrium) and minority (metastable) phases. The latter correspond to two different stacking sequences of close-packed layers, and their relative contributions to the thermal data correlate well with high temperature x-ray powder diffraction results. The upper (long axis tumbling) transition in the majority phase exhibits 50 K supercooling when scanned at 2 K/min. C60 impurities at the few % level depress the transition temperatures substantially.